The invention is directed to a flexible hose pump having rotating rollers, in which a hose, arranged in a partial circular housing wall portion, is sequentially, transversely compressed in a contact area.
In such a hose pump, the length of the partial circle is selected to correspond with the number of rollers to sequentially produce, in all phases of the rotation, a closed hose chamber. In the arrangement of two rollers, the partial circle corresponds, in form to a semi-circle, in the course of the operation of an arrangement of three rollers displaced at similar angles with respect to each other, a partial circle in the form of a third of a circle suffices.
With existing flexible hose pumps of this type, it is known to employ flexible hoses having a circular formed cross-section. A shortcoming of this known arrangement is that the hoses are exposed to considerable abrasion in the compression resulting from the passage of the rollers. This wear occurs because, by the squeezing action of the compression, both the outerlying hose walls as well as the inner-lying hose walls, are exposed to tension and tangential stresses. The inner-lying hose walls are moved through the rollers by their passage in a direction toward the discharge side, specifically, the rollers attempt to move the inner-lying hose walls in the direction of the discharge side, whereby these hose walls, in the portion lying in front of the rollers, are compressed and, in the portion following the rollers, are stressed in tension. In a corresponding manner, the outer hose walls are stressed in the contact region. The stresses take effect very strongly and are increased by the moment resulting from the difference between the hose inner diameter and the hose outer diameter. This moment is relatively large in a hose with a circular cross-section. A further disadvantage of the known hose pumps is that with a discharge delivery at the discharge or pressure side after the raising of the respective roller from the hose inner wall, the hose chamber formed between the two rollers opens to the pressure side, so that a part of the pressurized advancing fluid can run back in the rear end of the chamber enlarged through the raising of the roller. This results in non-uniform delivery and disadvantageous vibrations.